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A/C blower issue?

Tiny
BHAMDOC1973
  • MEMBER
  • 2008 MERCEDES BENZ S550
  • V8
  • 4WD
  • AUTOMATIC
  • 181,000 MILES
The temperature of the air coming out of vents is always super cold, so no issues there. Blower speed changes on its own. I can drive and it goes from say a 1 with very little air coming out to 7 which is max on otw own. Stays for about 30 seconds then toes back to 1. While it's on 7 I can adjust the speed to 6 or 5 or whatever I need. Trying to see if this is a blower or a resistor issue.
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Monday, July 25th, 2022 AT 8:18 PM

9 Replies

Tiny
SQM
  • MECHANIC
  • 6,383 POSTS
Hello,

Does this only happen when it is in Auto mode?
If so, the issue is the inside temperature sensor. It is not able to report proper temperature and the fan is just trying to achieve the set temperature by going from low to high.
This is part of the HVAC module.

I had the same issue with my CLK and just ended up using the manual mode to bypass the issue.

Let me know of any questions.
Thank you.
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Monday, July 25th, 2022 AT 10:06 PM
Tiny
BHAMDOC1973
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It does that not when it's in Auto mode. I thought about it, but when you do it in automate I don't think it will do it but I also don't think it would cool. I never understand Auto-mode fully, so does this mode control the speed of the blower as well as the temperature of the air coming out? Or just temperature. I will try again and see.
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Tuesday, July 26th, 2022 AT 7:28 AM
Tiny
BHAMDOC1973
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  • 1,291 POSTS
Tried auto option and same thing. Just randomly goes from high to cough a bit then down to 1 or none.
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Tuesday, July 26th, 2022 AT 8:21 AM
Tiny
BHAMDOC1973
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  • 1,291 POSTS
This.
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Wednesday, July 27th, 2022 AT 1:12 PM
Tiny
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  • MECHANIC
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Were you able to fix the wire? It really looked like the issue is that wire.
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Thursday, July 28th, 2022 AT 8:56 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,291 POSTS
I ordered another one. These are not serviceable.
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Friday, July 29th, 2022 AT 12:44 AM
Tiny
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Let me know how it turns out.
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Friday, July 29th, 2022 AT 4:13 PM
Tiny
BHAMDOC1973
  • MEMBER
  • 1,291 POSTS
It was the motor assembly. Thank you
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Friday, July 29th, 2022 AT 5:22 PM
Tiny
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Glad you got it figured out!
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Friday, July 29th, 2022 AT 8:19 PM

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